Oxygen Saturation from pO2
All calculations should be independently verified prior to clinical use. These calculators are intended to supplement, not replace, clinical judgment.
Estimate hemoglobin oxygen saturation (SaO2) from the partial pressure of oxygen (pO2) using the Severinghaus equation. Assumes standard temperature (37°C), pH 7.40, and normal 2,3-DPG.
The calculation uses the Severinghaus (1979) equation, which provides a close approximation to the oxyhemoglobin dissociation curve under standard physiological conditions:
This estimate does not account for shifts in the dissociation curve due to temperature, pH, or 2,3-DPG concentration (the Bohr effect). Acidosis, fever, and elevated 2,3-DPG all shift the curve rightward (lower affinity, higher pO2 needed for the same saturation); alkalosis, hypothermia, and reduced 2,3-DPG shift it leftward.
Landmark values on the standard oxyhemoglobin dissociation curve:
| pO2 (torr) | SO2 (%) | Note |
|---|
See also the Oxygen Content and A-a Gradient calculators.
References
- Severinghaus JW. Simple, accurate equations for human blood O2 dissociation computations. J Appl Physiol. 1979;46(3):599–602.
- West JB. Respiratory Physiology: The Essentials. 9th ed. Lippincott Williams & Wilkins; 2012.